Recent increases in HIV diagnoses, sexually transmitted infections, and risk behavior indicate that research is needed to identify effective positive prevention interventions integrated within HIV primary care settings to reduce transmission risk behavior among HIV positive individuals. In particular, no effective interventions exist for those newly diagnosed. The time period after HIV diagnosis may be a `teachable moment'to motivate reductions in risk behavior or maintenance of lower risk. This is a window of opportunity, as the first year after receiving an HIV diagnosis may be a critical period for risk reduction, especially for men. The primary objective of this study is to evaluate the efficacy of a brief positive prevention intervention, based on the Information, Motivation and Behavioral Skills (IMB) Model, provided within the care and treatment of newly diagnosed HIV-positive men who have sex with men (MSM) to reduce transmission risk behavior. The proposed five-year study will randomly assign 300 sexually active, HIV- positive MSM, newly diagnosed within the prior 3 months, to receive either 1) comprehensive standard of care (CSC) or 2) Brief Risk Reduction + CSC (BRR), a brief individual intervention based on the IMB model that addresses sexual transmission risk behavior and substance use. BRR will follow the initial physician visit and integrate risk reduction in the context of personalized and relevant medical treatment to enhance the uptake of health-protective information. Assessments of information, motivational influences, behavioral skills, sexual risk behavior, and substance use will be collected at baseline, post-intervention (3-), and 6-, 9-, 12- month follow-up points to determine intervention outcome effects. It is hypothesized that, relative to newly diagnosed HIV- positive men assigned to the comparison condition (CSC), those in the BRR intervention will exhibit significantly lower rates of HIV sexual transmission risk behavior, delayed onset to first unprotected sexual activity, and reduced substance use. Over time, reductions in transmission risk behaviors will be predicted by key elements of the IMB model and will demonstrate mediation of intervention effects. If successful, this research will identify a brief positive prevention intervention that can be implemented in the care setting for newly HIV diagnosed men. PUBLIC HEALTH RELEVANCE Research is needed to identify effective positive prevention interventions that can be integrated within HIV treatment settings to reduce risk behavior among HIV positive individuals. This research will be the first to evaluate a brief risk reduction intervention to reduce transmission risk behavior among newly HIV diagnosed men, with scientific relevance regarding whether intervening early after an HIV+ diagnosis maximizes a `teachable moment'for risk reduction. The proposed intervention research is significant and highly relevant to the public health, due primarily to the importance of targeting those newly diagnosed. Intervening early after the HIV diagnosis focuses on a time period that may have increased likelihood of HIV transmission due to fluctuating levels of risk behavior as one adjusts to the diagnosis, provides an opportunity to maintain risk reduction initiated after learning of HIV+ status, and assists in the transition to medical care through inclusion of risk reduction in a multidisciplinary approach to care.